At 6.30 a.m. on Monday morning, before it is even fully light, Dot Bruce is hard at work putting the finishing touches to the first day back in business at the Park Road Lido — an outdoor swimming pool in London. (Park Road is heated — less than an indoor pool, but many lidos have no heating at all.)

Dot, as she's known to everyone at the lido, is the assistant manager at Park Road, and knows that today calls for something special. That includes a bright pink sash — like something a homecoming queen might wear — fluttering over the lido's gates. It reads "Grand Opening," in sparkly letters.

"It's just to make things a little more exciting, although, it should actually say 'Grand Reopening,'" she says.

For the last five months, Britain has been living under its strictest, legally mandated lockdown yet since the start of the pandemic. But now, as vaccination rates have risen and death rates have fallen, a gradual unlocking has begun, starting with outdoor leisure facilities. That includes lidos — a very British institution — some heated, some definitely not.

Dot has been working hard for this moment for weeks. There were leaks in the pool that needed to be repaired, and months of dead leaves to clear. By today, things are finally ready, though.

She has even given the pool a test drive: "I swam on Saturday to give it a little test out, and it's beautiful. It really is amazing."

A few minutes later, before the gates are even open, the first swimmers begin arriving. This being London, everyone forms an orderly queue. Conversations break out — have you had your jabs? What will the temperature be like?

Across Britain, at the very same moment, this same scene is being repeated outside outdoor pools up and down the country. Lidos, and outdoor swimming in general, have a cult following in Britain, despite, or perhaps because of, the climate and weather.

Most lidos were built before World War II as part of a push to improve the health of the population and ensure all children were taught to swim. Park Road was part of this campaign. In its early days, there were diving boards and a chip (French fries) shop across the road. Apparently, you could even have a cup of tea delivered poolside.

After the war, lidos fell out of favor as heated indoor pools became the norm, and summer vacations in warmer countries became more affordable. But in the last decade, that has been changing, and outdoor swimming of all types has seen a big revival.

COVID-19 and lockdowns put a temporary stop to that. The closures of lidos have been particularly hard on those who rely on them for mental and physical health. Not to mention community.

At Park Road, Hesketh Benoit is one of the early arrivals standing in line. "I'm here for the grand opening — or grand reopening," he says. "I've got this cold water buzz — I've actually been missing it like hell. Like hell, like hell!"

Once the gates open, there's a dignified rush into the poolside area. It does look otherworldly: clear, blue water ringed with red tiles, enclosed by dense pine trees and hedgerows. Birds swoop across the deep end, unused to human intrusion after so many months.

Two regulars haven't shown up yet: the lido's two resident ducks, known as Park and Road. They usually land near the deep end and do a few lengths in the afternoon. Both have honorary, lifetime membership.

Hesketh is part of the first wave of humans in the water. How is it?

"Beautiful! Beautiful!"

He sweeps his arms across the pool as the other bathers pile in.

"Look at this business. Absolutely. Arms going, legs going — my mate Adrian here is a pensioner, he's in. Well, I'm a pensioner too, come to that!"

Like any tribe, the lido swimmers have their leader: Katy Ferguson is the chair of the Park Road Users Groups, now hundreds of members strong. Standing by the pool, she says the group has gotten so big, it's hard to remember all the names, but she does recognize the faces.

"People look really happy. They really do. They are just so pleased," she says.

During the lockdown, she started jogging, but never really took to it.

"Jogging? It's a much less friendly experience. Whereas swimming? Swimmers tend to be nice. They do."

And she and the other swimmers can attest, dipping into the lido after so long — after the first shock of cold — it is glorious. One chapter of lockdown is, for now, over.

This article originally appeared at The World. Follow them on Twitter.